Leukemia-associated Rho guanine nucleotide exchange factor, a Dbl family protein found mutated in leukemia, causes transformation by activation of RhoA
Leukemia-associated Rho guanine nucleotide exchange factor, a Dbl family protein found mutated in leukemia, causes transformation by activation of RhoA
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DOI：
10.1074/jbc.m103565200
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发表时间：
2001-07-20
影响因子：
4.8
通讯作者：
Der, CJ
中科院分区：
文献类型：
--
作者：
Reuther, GW;Lambert, QT;Der, CJ
白血病相关Rho鸟嘌呤核苷酸交换因子（LARG）最初被确定为急性髓系白血病患者混合谱系白血病的融合伙伴。LARG具有串联Dbl同源和pleckstrin同源结构域结构，因此可能作为Rho GTPases的激活剂。在这项研究中，我们证明了LARG是一个功能性的Dbl蛋白。细胞中LARG的表达引起血清反应因子的激活，这是rho介导的信号通路的已知下游目标。LARG的短暂过表达不会激活细胞外信号调节激酶或c-Jun nh2末端激酶有丝分裂原激活的蛋白激酶级联，这表明LARG不是Ras， Rac或Cdc42的激活剂。我们进行了体外交换实验，分离的LARG的Dbl同源（DH）或DH/pleckstrin同源结构域作为RhoA的强激活剂，但对Rad或Cdc42没有活性。我们发现LARG可以在体外与RhoA复合物，但不能与Rac或Cdc42复合物，并且LARG的表达导致RhoA激活的gtp结合形式的水平增加，而在体内则不会增加Rad或Cdc42。因此，我们得出结论，LARG是rhoa特异性鸟嘌呤核苷酸交换因子。最后，与活化的RhoA一样，我们确定LARG与活化的Raf-1协同转化NIH3T3细胞。这些数据表明LARG是第一个在癌症中突变的功能性Dbl蛋白，并表明LARG介导的RhoA激活可能在人类白血病的发展中发挥作用。
Leukemia-associated Rho guanine nucleotide exchange factor (LARG) was originally identified as a fusion partner with mixed-lineage leukemia in a patient with acute myeloid leukemia. LARG possesses a tandem Dbl homology and pleckstrin homology domain structure and, consequently, may function as an activator of Rho GTPases. In this study, we demonstrate that LARG is a functional Dbl protein. Expression of LARG in cells caused activation of the serum response factor, a known downstream target of Rho-mediated signaling pathways. Transient overexpression of LARG did not activate the extracellular signal-regulated kinase or c-Jun NH2-terminal kinase mitogen-activated protein kinase cascade, suggesting LARG is not an activator of Ras, Rac, or Cdc42, We performed in vitro exchange assays where the isolated Dbl homology (DH) or DH/pleckstrin homology domains of LARG functioned as a strong activator of RhoA, but exhibited no activity toward Rad or Cdc42. We found that LARG could complex with RhoA, but not Rac or Cdc42, in vitro, and that expression of LARG caused an increase in the levels of the activated GTP-bound form of RhoA, but not Rad or Cdc42, in vivo. Thus, we conclude that LARG is a RhoA-specific guanine nucleotide exchange factor. Finally, like activated RhoA, we determined that LARG cooperated with activated Raf-1 to transform NIH3T3 cells. These data demonstrate that LARG is the first functional Dbl protein mutated in cancer and indicate LARG-mediated activation of RhoA may play a role in the development of human leukemias.